Telephone-exchange system



D. M. TAGGART.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV- n, 1911.

1 12,768. Patented Aug. 12,1919.

7 To all whom it may concern:

UNITED STATES PATENT OFFICE. V

DAWSON M. Tacoma, or EAST canton, NnW Ens Y, nssreivoa T0 ELECTRICCOMPANY, INCORPORATED, or NEW YORK, 11:, A CORPORATION on EW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed November 1 7, 1917. Serial No; 202,515.

Be it known that I, DAWSON M. TAGGART, a citizen of the United States,residing at East Orange, in the county of Essex and State of New Jersey,have invented certain new and useful Improvements in Telephone- ExchangeSystems, of which the following is a full, clear, concise, and exactdescription.

This invention relates to telephone exchange systems,- and moreparticularly to such systems as the central energy type.

Theobject of the invention is to provide 7 improved signalin means forsuch systems.

In accordance w1th the feature of this invention, apparatus associatedwith a link circuit connected with a telephone line functions upon theopening and subsequent closure of the tele hone line to cause theintermittent operation of a signalin device which is common to aplurality of link circuits, thereby to furnish a recall signal to a thisinvention, reference should-be had to the following descriptionconsidered in connection with the accompanying drawing illustrating oneembodiment of this invention, and wherein there are shown two tele phonelines A and B which maybe connected through a link circuit C.. It is tobe understood that many lines similar to A a and B may terminate at thesame central oflice and that a plurality of link circuits similar to Cmay be employed for interconnecting such lines. The apparatus shownwithin the dotted rectangle 5 is common to a plurality of. link,circuits. It-is thought .that the nature of this invention is such thata complete understanding thereof may.

be had from a description of the operation of the system disclosed inthe drawing, and

it will be so described. I

Subscriber A, in initiating a call, removes the receiver from. theswitchhook, thereby causing the lighting of line'lamp 6 in the 'usualmanner. The'operator, upon observing the lighted condition of the linelamp 6,

inserts answering plug 7 of cord circuit G into line jack 8, whereuponcutoff relay 9 and supervisory relay 10 operate, Answerright-hand normalcontact '0 tact thereof, contact of supervisory relay .10, left-handalternate contact of relay 15, resistance coil 16, sleeve contacts ofthe ing of cutoff relay 9' to ing supervisory 'lamp 11 is not lighted atthls tune for the reason that a low resistance shunt, lncluding aresistance coil 12 and the left-hand winding ofrelay 13-isestablishedtherefor by the operation of the superyisory relay 10. p The left-handwindmg of relay 13 is of low resistance, while its right-hand winding isof high resistance, the urpose of which will more fully hereinafterappear. The establishment of this shuntcircuit about the lamp 11 causesthe operation of the relay 13 over a circuit from battery through thecontact of switch 14, left-hand 'windin of relay 13,

f relay 15, contact of supervisory relay 10, left-hand normal contact ofrelay 15, resistance coils 12' and 16, sleeve contacts of the answeringplug 7 andjack 8, and the winding of the cutoff relay 9 to ground. Theoperation of relay 13 connects an interrupter 17 in circuit with a pilotlamp 18, thereby causing the intermittent operation thereof. This pilotlamp 18 is common to a plurality of link circuits. The intermittentoperation of this pilot lamp is an indication to the operator that someaction upon her part is-required in establishing a connection.

The operator thereupon actuates listening key 20, causing the operationof relay 15, over 7 a circuit from battery-through the right-handwinding thereof and the contact of listening establishes a lockingcircuitfor itself from battery through the right-hand alternateconanswering plug 7 and jack 8, and the windmind. The opera tion ofrelay 15 opens the hereinbefore-men- I tioned shunt circuit, whichincludes the low resistance'winding of relay 13, and substitutesthereforanother shunt circuit includingfthe left-hand windlngof the relay 15,.100

which is in the locking circuit of relay 15.

The left-hand winding of relay 15'is of low resistance to prevent thelighting of the answering supervisory lamp 11. The opening 7 of thefirst-mentioned shunt circuit releases 105 the common relay 13,whereupon the pilot lamp 18 is extinguished. V

The operator, upon'bemg advised that the connection is desired with theline of subscriber B,restores the listening key '26 to, 110

PatentedAug. 12,1919. 7

normal position and inserts calling plug 21 in line jack 22, whereuponcalling supervisory lamp 23 is lighted and cutoff relay 2% operated.Subscriber B may be signaled by the operation of the usual ringing key25 and, upon responding to the operation of the call bell, the removalof the receiver from the 'switchhook causes the operation of callingsupervisory relay 30. Upon the operation of this supervisory relay 30, ashunt circuit, including resistance coil 31, is established for andextinguishes the lamp 23.

Upon the conclusion of the conversation, the subscribers restore thereceivers to the switchhooks, whereupon the answering and callingsupervisory relays 10 and '30 are deenergized to open the shunt circuitsabout the answering and callinglamps 11 and 23, whereupon these lampsare lighted to furnish disconnect signals.- The deenergization of theanswering supervisory relay 10 also opens the locking circuit for therelay 15, which thereupon releases its armatures. If, before the plugsare withdrawn from the jacks, the calling subscriber A desires toinitiate another call, the mere removal of the receiver from theswitchhook causes the intermittent operation of the pilot lamp 18, dueto the operation of the common relay 13 upon the energization of theanswering supervisory relay 10. The operation of the supervisory relay10, in closing the energizing circuit through the left-hand lowresistance windingof the common relay 18, also thereby establishes thelow resistance shunt circuit including the resistance-12, whereupon theanswering supervisory lamp 11 is extinguished. The operator, then, uponobserving the flashing of the pilot lamp 18, may actuate the commonswitch 14, thereby opening the contact thereof and removing a shortcircuit of the high resistance righthand winding of relay 13. This highresistance winding is then included in the shunt circuitrabout the lamp11, thereby making this shunt circuit of such high resistance that thelamp 11 will be lighted. In this manner, the operator may definitelydetermine which of several engaged cord circuits is connected with theline which has initiated a recall. The key 1 1 may now be restored tonormal position, and the listening key 20 actuated to connect theoperator with the line upon which the recall has been made. If anotherconnection is desired, this may be completed in the usual manner.

When both supervisory lamps are lighted a disconnect signal is furnishedthe operator, who may thereupon withdraw the plug from the jacks andrestore all apparatus to normal condition. 7

What is claimed is:

1. A telephone exchange system comprising telephone lines, a pluralityof link circuits for interconnecting the lines, one of which isconnected with one of the lines, a

supervisory relay and a signaling device in the engaged link circuit, asignal device common to the link circuits, means controlled by thesupervisory relay and rendered effective upon the opening and subsequentclosure of the engaged line to cause the operation of the commonsignaling device, a normally ineffective energizing circuit for thesignaling device individual to the engaged link circuit, and a switchactuated subsequent to the operation of the common signaling device forrendering the energizing circuit effective for energizing the individualsignaling device.

2. A telephone exchange system comprising telephone lines, a pluralityof link circuits for interconnecting the lines, one of which isconnected with one of the lines, a supervisory relay and a signalingdevice in the engaged link circuit, a signaling device common to thelink circuits, a relay responsive to the opening of the telephone line,a relay responsive to the subsequent closure of the telephone line andcooperating with the second-mentioned relay to cause the intermittentoperation of the signaling device when the supervisory relay isenergized, a normally ineffective energizing circuit for the signalingdevice individual to the engaged link circuit, and a switch actuatedsubsequent to the operation of the common signaling device for renderingthe energizing circuit eflective for energizing the individual signalingdevice.

3. A telephone exchange system comprising telephone lines, a pluralityof link circuits for interconnecting the lines, one of which isconnected with one of the lines, a supervisory relay and a signalingdevice in the engaged link circuit, a signaling device common to thelink circuits, a relay individual to the engaged link circuit responsiveto the opening of the telephone line, a relay common to a plurality oflink circuits responsive to the subsequent closure of the telephone lineand cooperating with the individual relay to cause the intermittentoperation of the common signaling device while the supervisory relay isenergized, a

normally inefiective energizing circuit for the signaling deviceindividual to the engaged link circuit, and a switch actuatedsubsequentto the operation of the common signaling device for renderingthe operating circuit effective for energizing the individual signalingdevice.

4. A telephone exchange system comprising telephone lines, a pluralityof link circuits for interconnecting the lines, one of which isconnected with one of the lines, a supervisory relay and a signalingdevice in the engaged link circuit, an operators telephone set, alistening key for connecting the operators telephone set to the engagedlink circuit, a relay individual to the engaged energization of both thesupervisory and individual relays followed by the energization of thesupervisory relay, and interrupter mechanism brought into circuit withthe common signaling device by the energization of the common relay.

5. A telephone exchange system comprising telephone lines, a pluralityof link circuits for interconnecting the lines, one of which isconnected with one of the lines, a supervisory relay controlled overthe. engaged telephone line, a supervisory lamp in the engaged linkcircuit, a signaling device common to the link circuits, means con-jtrolled by the supervisory relay and rendered effective upon the openingand subsequent closure of the engaged line to cause the operation of thecommon signaling device, and a switch subsequently actuated to cause thelighting of the supervisory lamp.

6. A telephone exchange system comprising telephone lines, a pluralityof link circuits for interconnecting the lines, one of which isconnected with one of the lines, a supervisory relay controlled over theengaged line, a supervisory lamp in the engaged link circuit, a lampcommon to the link circuits, a relay individual to the engagedlinkcircuit responsive to the deenergization of the supervisory relaywhen the engaged line is open, a relay common to the link c1'rcu1tsresponsive to the subsequent energization of the supervisory relay uponthe I closure of the engaged line and cooperating with the individualrelay to cause the'light ing of the common lamp, and a switch subsequently actuated to cause the lighting of the supervisory lamp. 7

7. A telephone exchange system comprising telephone lines, a pluralityof link circuits for interconnecting the lines, one of which isconnected With one of the lines, a supervisory relay and a signalingdevice in the engaged link'circuit, a normally inefi'ec-,

tive energizing circuit for the signaling device rendered effective bythe deenergization of the supervisory relay and inefiective by theenergization thereof, a signaling device common to the link circuits, arelay individual to the engaged link circuit responsive to thede'energization of the supervisory relay, a relay common to the linkcircuits responsive to the subsequent energization of the supervisoryrelay and cooperating With the individual relay to cause the operationof the common signaling device, and a switch subsequently actuated torender the energizing circuit of the individualsignaling deviceefiective While the supervisory relay is energized. I

In witness whereof, I hereunto subscribe my name this 14th day ofNovember A. D.,

' DAWSON M. TAGGART.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents,

Washington, D. C.

